In Greek mythology, Chaos or Khaos is the primeval state of existence from which the first gods appeared. In other words, the dark void of space. It is made from a mixture of what the Ancient Greeks considered the four elements: earth, air, water and fire. For example, when a log is burned, the flames were attributed to the fire in it, the smoke the air in it, the water and grease that come from it were supposed to be the water, and the ashes left over were the earth.

Ovid, in his Metamorphoses, described Chaos as "rather a crude and indigested mass, a lifeless lump, unfashioned and unframed, of jarring seeds and justly Chaos named". From that, its meaning evolved into the modern familiar "complete disorder".

Chaos features three main characteristics:

* it is a bottomless gulf where anything falls endlessly. This radically contrasts with the Earth that emerges from it to offer a stable ground.
* it is a place without any possible orientation, where anything falls in every direction;
* it is a space that separates, that divides: after the Earth and the Sky parted, Chaos remains between both of them.

Theogonia

According to Hesiod's Theogonia (The origin of the Gods), Chaos was the nothingness out of which the first objects of existence appeared. These first beings, described as children of Chaos alone, were Gaia (the Earth), Tartarus (the Underworld), Nyx (the darkness of the night), Erebus (the darkness of the Underworld), and Eros (sexual love). From these beings and the first generation of beings created by them, Hesiod establishes the deities related to each element known to early Greeks, beginning with the primordial elements: the Earth, the starry Sky (Ouranos), and the Sea (Pontus).

Theogonia presents two ways to come to life: division (Gaia, Nyx) and mating. After Gaia, almost all deities brought to life by division are negative concepts (Death, Distress, Sarcasm, Deception, and so on) and for the most part are produced by the goddess Nyx. From this point on is set the model for reproduction, from the action of two entities, male and female, as it appears in the divine world in response to human society. So the first answer by the myth to the question "What is the cause of this?" becomes "This is the father and this is the mother".

Primal Chaos

In Ancient Greek cosmology, Chaos was the first thing to exist and the womb from which everything emerged. For Hesiod and the Olympian mythos, Chaos was the 'vast and dark' void from which the first deity, Gaia, emerged. In the Pelasgian creation myth, Eurynome ('goddess of everything') emerged from this Chaos and created the Cosmos from it[citation needed]. For Orphics, it was called the 'Womb of Darkness' from which the Cosmic Egg that contained the Universe emerged. It is sometimes conflated with 'Black Winged Night'.

The idea is also found in Mesopotamia and associated with Tiamat the 'Dragon' of Chaos, from whose dismembered body the world was formed.

Genesis refers to the earliest conditions of the Earth as "without form and void," a state similar to chaos.

Primal Chaos was sometimes said to be the true foundation of reality, particularly by philosophers such as Heraclitus and those trained in Orphic schools. It was the opposite of Platonism. It was also probably what Aristotle had in mind when he developed the concept of Prima Materia in his attempt to combine Platonism with the Presocraticism and Naturalism. It was a concept inherited by the theory of Alchemy.